Peanut butter oatmeal cookies packed with M&M’s and chocolate chips. These monster cookies are incredibly soft, chewy, thick, and so easy to make! 

Monster cookies on a plate with more cookies and milk on the side.

What Are Monster Cookies?

Say hello to one of my favorite cookie creations, these incredibly soft and chewy monster cookies! If you’ve never had a monster cookie, then I think you’ll adore these cookies that are jam-packed with tons of goodies.

Originally published in September of 2017, this is still the same delicious cookie recipe. However, I’ve updated this post with more step pictures, information, and better instructions so that you can easily whip up a batch of these cookies.

Bonus: you don’t even have to chill this cookie dough. That means you can be enjoying soft, warm cookies in about 30 minutes!

Monster cookies are essentially peanut butter oatmeal cookies with chocolate chips and M&M’s. It’s kind of like three different cookies all packed into one. 

You can also make monster cookies different ways, like with milk chocolate chips or Reese’s Pieces instead of M&M’s. However you make them, they’re one of the most delicious cookie recipes you’ll ever try!

Recipe Ingredients 

This is essentially a recipe for peanut butter oatmeal chocolate chip cookies. Can you say “yum?” Here’s what you’ll need to make these oatmeal monster cookies:

  • All-Purpose Flour: The base of any good cookie recipe starts with some flour. Just make sure you spoon and level your flour into the measuring cup so you don’t end up with crumbly cookies.
  • Baking Soda & Salt: The baking soda provides a little lift while the salt balances out the sweetness of the dough. 
  • Old-Fashioned Rolled Oats: I suggest sticking with old-fashioned rolls oats in these cookies because they make them chewier! Quick oats would probably be fine too, just keep in mind that they’re pressed thinner and won’t provide the same level of chewiness. 
  • Unsalted Butter: As always, I prefer to stick with unsalted butter in my cookie recipes. This allows you to control the amount of salt going into your cookies.
  • Brown Sugar & Granulated Sugar: I love to use a mix of sugars in my cookies, the brown sugar adds flavor and moisture.
  • Peanut Butter: It’s best to stick with a thicker, no-stir peanut butter like Jif or Skippy.
  • Egg & Pure Vanilla Extract: There’s only one egg in this cookie dough and it helps to bind everything together. The vanilla extract adds a little extra flavor.
  • M&M’s and Semi-Sweet Chocolate Chips: You can easily switch up the flavor of these cookies by using another baking chip, different kinds of M&M’s, and so on. 

How To Make Monster Cookies

To make these monster cookies, you’ll start out by whisking together the flour, baking soda, and salt. Then, stir in the old-fashioned rolled oats until fully combined.

Next, you’ll cream together your butter, brown sugar, and granulated sugar for 1 to 2 minutes or until they’re well combined. Once the butter and sugar are thoroughly mixed together, mix in the peanut butter, egg, and vanilla extract. I also recommend stopping to scrape down the sides of your bowl, and mixing again to ensure that all of the wet ingredients are well combined.

A glass bowl filled with monster cookie dough on top of a marble surface.

Once you’ve mixed up the wet and dry ingredients, you’ll combine them and then stir in your chocolate chips and M&M’s. At this point, you can scoop the cookie dough onto baking sheets and bake the cookies or refrigerate/freeze it until you’re ready. I like to use a 1.5 tablespoon cookie scoop because it creates the perfect size cookies!


How do you make these cookies soft?

To create soft oatmeal M&M’s cookies, you want to avoid overbaking them. The tops will be set, but they will still be soft when you remove them from the oven. The cookies will continue to firm up from the residual heat of the baking sheet and as they cool. 

Tip: Store the cookies in an airtight container with a slice of bread. This will help them stay soft for days!

Can you freeze them?

Yes! You can freeze the balls of cookie dough or baked peanut butter oatmeal chocolate chip cookies that have cooled completely for up to 3 months. You can bake frozen cookie dough balls for an additional 1 to 2 minutes, no need to thaw the cookie dough. For the baked cookies, you’ll want to thaw them to room temperature on the counter before serving.

How can you tell when the cookies are done?

The edges and tops of the cookies will look set and no longer doughy. I find that about 10 to 11 minutes at 350°F (177°C) is the perfect amount of time for these cookies. 

Baked monster cookies lined up on a piece of parchment paper.

Baking Tips 

  • When measuring your flour, make sure to spoon it into the measuring cup and level it off with the back of a knife.
  • Using a natural peanut butter where the oil separates will cause these cookies to spread more and turn out greasy. I suggest sticking with a thicker, no-stir peanut butter like Jif or Skippy. 
  • Make sure to stick with old-fashioned oats, this will create a much chewier oatmeal cookie!
  • Feel free to swap out the semi-sweet chocolate chips for dark chocolate or milk chocolate chips and the M&M’s for Reese’s Pieces.  

More Classic Cookie Recipes to Try!

A stack of monster cookies on a speckled plate.

Soft and Chewy Monster Cookies

5 from 17 ratings
Prep Time: 15 minutes
Cook Time: 12 minutes
Total Time: 27 minutes
Peanut butter oatmeal cookies packed with M&M's and chocolate chips. These monster cookies are incredibly soft, chewy, thick, and so easy to make!


Servings: 32 cookies
  • 1 cup (125 grams) all-purpose flour , spooned & leveled
  • 1 1/4 cups (125 grams) old-fashioned rolled oats
  • 1/2 teaspoon baking soda
  • 1/4 teaspoon salt
  • 1/2 cup (115 grams) unsalted butter , softened
  • 3/4 cup (150 grams) brown sugar , lightly packed
  • 1/4 cup (50 grams) granulated sugar
  • 1/2 cup (125 grams) creamy peanut butter
  • 1 large egg , room temperature
  • 1 teaspoon pure vanilla extract
  • 3/4 cup (150 grams) M&M's
  • 1/2 cup (95 grams) semi-sweet chocolate chips


  • Preheat oven to 350°F (177°C). Line two large baking sheets with parchment paper or silicone baking mats and set aside.
  • In a large mixing bowl, whisk together the flour, old-fashioned rolled oats, baking soda, and salt. Set aside.
  • In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a handheld mixer, cream together the butter, brown sugar, and granulated sugar for about 1-2 minutes or until well combined. Mix in the peanut butter, egg, and vanilla extract until fully combined, making sure to stop and scrape down the sides of the bowl as needed.
  • Slowly mix in the dry ingredients until just combined. Add the M&M's and chocolate chips and gently fold them into the cookie dough.
  • Using a 1.5 tablespoon cookie scoop, scoop balls of cookie dough onto the prepared baking sheets, making sure to leave a little room between each one.
  • Bake in separate batches at 350°F (177°C) for 10-12 minutes or until the tops of the cookies are set. Remove from the oven and allow to cool on the baking sheet for 5-10 minutes, then transfer to a wire rack to cool completely. 


Peanut Butter: It's best to use a no-stir creamy peanut butter like Jif or Skippy for these cookies.
Egg: To get your egg to room temperature quickly, place it in a bowl of warm water for 5-10 minutes.
Storage Instructions: Store cookies in an airtight container on the counter for up to 5 days.
Freezing Instructions: Scoop balls of the cookie dough onto a baking sheet lined with parchment paper. Freeze for several hours or until the cookie dough is completely frozen, then store in a freezer bag or container. Cookie dough balls may be baked from frozen for an additional 1-2 minutes.
Baked cookies will also freeze well for up to 3 months. Thaw to room temperature on the counter before serving.
Cuisine: American
Course: Dessert
Author: Danielle
Did you make this recipe?Mention @livewellbakeoften on Instagram or tag #livewellbakeoften.